It is known practice to dye keratin fibres, and in particular human hair, with dye compositions containing oxidation dye precursors, generally known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidation bases are generally combined with couplers. These bases and these couplers are colourless or weakly coloured compounds which, when combined with oxidizing products, can give rise to coloured compounds via a process of oxidative condensation. This type of oxidizing dyeing makes it possible to obtain permanent colourings, but it causes a degradation of the keratin fibres owing to the use of oxidizing agents.
Moreover, it is known practice to dye keratin fibres, and in particular human hair, with dye compositions containing direct dyes. Conventional dyes which are used are in particular dyes of nitrobenzene, anthraquinone, nitropyridine, azo, xanthene, acridine, azine or triarylmethane type or natural dyes. These dyes are coloured or colouring molecules which have a certain affinity for keratin fibres.
The compositions containing one or more direct dyes are applied to the keratin fibres for a period of time necessary to obtain the desired colouration, and are then rinsed out. The resulting colourations are particularly chromatic colourations which are, however, temporary or semi-permanent since the nature of the interactions that bind the direct dyes to the keratin fibre, and their desorption from the surface and/or from the core of the fibre, are responsible for their poor dyeing power and their poor fastness with respect to washing or perspiration.
Nowadays, hair dyeing processes using natural products are increasingly appreciated by users.
It is known practice, from document FR 2 549 721, to use natural dyes for hair dyeing. However, the process described still remains to be improved in terms of efficiency.
There is therefore a real need to develop hair dyeing processes which result in powerful colourations which are relatively nonselective, which are resistant to external agents (light, bad weather, shampooing), and which respect the nature of the hair, using compositions containing natural dyes.